part 1: overview of cogeneration and its status in asia - Fire

The concept of cogeneration 5
incur operation and maintenance costs while contributing practically nothing to reduce the
overall energy bill of the site.
Since these generators serve the main purpose of assuring emergency power to priority
areas of the site, no financial analysis is carried out to assess their economic viability.
However, these generators offer the possibility of continuous power generation so that the
monthly power bill of the site can be reduced. Such benefits accrued can well justify the need
for higher investment that is associated with prime movers which are designed to operate
continuously and at higher efficiencies.
In a gas turbine or reciprocating engine, typically a third of the primary fuel supplied is
converted into power while the rest is discharged as waste heat at a relatively high
temperature, ranging between 300 and 500ºC. At sites having a need for thermal energy in
one form or the other, this waste heat can be recovered to match the quantity and level of
requirements. For instance, steam may be needed at low or medium pressures for process
applications. Any heat recovered from the exhaust gases of the prime movers will help to
save the primary energy that would have been otherwise required by the on-site conversion
facility such as boilers or dryers.
An ideal site for cogeneration has the following characteristics:
• a reliable power requirement;
• relatively steady electrical and thermal demand patterns;
• higher thermal energy demand than electricity;
• long operating hours in the year;
• inaccessibility to the grid or high price of grid electricity.
Typical cogeneration applications may be in three distinct areas:
a) Utility cogeneration: caters to district heating and/or cooling. The cogeneration facility
may be located in industrial estates or city centres;
b) Industrial cogeneration: applicable mainly to two types of industries, some requiring
thermal energy at high temperatures (refineries, fertilizer plants, steel, cement, ceramic
and glass industries), and others at low temperatures (pulp and paper factories, textile
mills, food and beverage plants, etc.);
c) Commercial/institutional cogeneration: specifically applicable to establishments having
round-the-clock operation, such as hotels, hospitals and university campuses.
1.4 Technical Options for Cogeneration
Cogeneration technologies that have been widely commercialized include extraction/back
pressure steam turbines, gas turbine with heat recovery boiler (with or without bottoming
steam turbine) and reciprocating engines with heat recovery boiler.
1.4.1 Steam turbine cogeneration systems
The two types of steam turbines most widely used are the backpressure and the extractioncondensing
types (see Figure 1.2). The choice between backpressure turbine and extractioncondensing
turbine depends mainly on the quantities of power and heat, quality of heat, and